Intervertebral spacer that dynamically promotes bone growth

An intervertebral spacer comprising:

• a monolithic spacer having an anterior portion, a posterior portion, a superior surface, an inferior surface angled with respect to the superior surface to restore lordosis, and an open center portion configured to receive bone graft;
• wherein said monolithic spacer is configured to be implanted in a space between adjacent vertebral bodies with the superior surface engaging a superior vertebral body and the inferior surface engaging an inferior vertebral body;
• a first flange extending upwards from the superior surface and configured to engage an anterior surface of the superior vertebral body;
• and
• a second flange extending downwards from the inferior surface and configured to engage an anterior surface of the inferior vertebral body,
• wherein the first flange and second flange together function as a bone plate,
• wherein the intervertebral spacer is split along the anterior portion between the first and second flanges and intersecting the superior and inferior surfaces to provide motion in the anterior/posterior direction of between 1 and 5 degrees;
• and
• wherein a portion of the intervertebral spacer is configured to act as a torsion spring to allow the anterior/posterior motion.